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Abstract:

Air flow ducts for improving the air flow within data processing units
are described herein. In some embodiments, a duct includes an inlet
portion and an outlet portion. An interior surface of the outlet portion
of the duct defines, at least in part, a portion of a flow path. The duct
is configured to be coupled to a printed circuit board within a data
processing unit such that a first portion of a cooling fluid can flow
within the flow path between the inlet portion of the duct and an
electronic device coupled to the printed circuit board. An exterior
surface of the outlet portion of the duct is configured to redirect a
second portion of the cooling fluid to a volume within the data
processing unit apart from the electronic device.

Claims:

1. An apparatus, comprising; a duct including an inlet portion and an
outlet portion, an interior surface of the outlet portion of the duct
defining, at least in part, a portion of a flow path, the duct configured
to be coupled to a printed circuit board within a data processing unit
such that a first portion of a cooling fluid can flow within the flow
path between the inlet portion of the duct and an electronic device
coupled to the printed circuit board, an exterior surface of the outlet
portion of the duct configured to redirect a second portion of the
cooling fluid to a volume within the data processing unit apart from the
electronic device.

2. The apparatus of claim 1, wherein: the outlet portion is a first
outlet portion; the flow path is a first flow path, the exterior surface
of the first outlet portion defining, at least in part, a first portion
of a second flow path; and the duct includes a second outlet portion, an
interior surface of the second outlet portion of the duct defining, at
least in part, a second portion of the second flow path, the duct
configured to be coupled to the printed circuit board such that a second
electronic device coupled to the printed circuit board is within the
second flow path.

3. The apparatus of claim 1, wherein a size of a portion of the flow path
within the outlet portion is greater than a size of the inlet portion of
the duct.

4. The apparatus of claim 1, wherein a flow area of the flow path within
the outlet portion is greater than a flow area of the inlet portion of
the duct.

5. The apparatus of claim 1, wherein: the electronic device is an optical
transceiver disposed within a cage configured to contain a plurality of
optical transceivers in a stacked configuration; and the outlet portion
of the duct defines an opening that is configured to be substantially
aligned with an opening defined by the cage.

6. The apparatus of claim 1, wherein the duct configured to be coupled to
the printed circuit board such that a portion of the printed circuit
board defines, at least in part, the portion of the flow path.

7. An apparatus, comprising: a duct including an inlet portion, a first
outlet portion and a second outlet portion, the first outlet portion
defining, at least in part, a portion of a first flow path, an exterior
surface of the second outlet portion of the duct defining, at least in
part, a portion of the first flow path, an interior surface of the second
outlet portion of the duct defining, at least in part, a portion of a
second flow path, the duct configured to be coupled to a printed circuit
board such that a first electronic device coupled to the printed circuit
board is within the first flow path and a second electronic device
coupled to the printed circuit board is within the second flow path, the
duct configured such that a first portion of a cooling fluid can flow
within the first flow path between the first electronic device and a
volume within the data processing unit apart from the second electronic
device, the duct configured such that a second portion of the cooling
fluid can flow within the second flow path between the inlet portion of
the duct and the second electronic device.

8. The apparatus of claim 7, wherein a flow area of a portion of the
second flow path within the second outlet portion is greater than a flow
area of a central portion of the duct, the central portion of the duct
disposed between the inlet portion and the second outlet portion.

9. The apparatus of claim 7, wherein: the second electronic device is an
optical transceiver disposed within a cage configured to contain a
plurality of optical transceivers in a stacked configuration; and the
second outlet portion of the duct defines an opening that is configured
to be substantially aligned with an opening defined by the cage.

10. The apparatus of claim 7, wherein the first electronic device is
disposed between the first outlet portion and second outlet portion.

11. The apparatus of claim 7, wherein: the second electronic device is an
optical transceiver disposed within a cage configured to contain a
plurality of optical transceivers in a stacked configuration; and the
second outlet portion of the duct includes a shroud defining an opening
facing a side wall of the cage, the shroud having a height greater than a
height of a central portion of the duct, the central portion of the duct
disposed between the inlet portion and the second outlet portion.

12. The apparatus of claim 7, wherein: the second electronic device is a
first optical transceiver disposed within a cage configured to contain a
plurality of optical transceivers such that the first optical transceiver
is disposed between a second optical transceiver from the plurality of
optical transceivers and the printed circuit board; and the second outlet
portion of the duct includes a baffle such that the second portion of the
cooling fluid can flow within the second flow path from the inlet portion
of the duct substantially in parallel to the first optical transceiver
and the second optical transceiver.

13. The apparatus of claim 7, wherein: the exterior surface of the second
outlet portion of the duct is configured to redirect the first portion of
the cooling fluid within the first flow path to the volume within the
data processing unit apart from the second electronic device.

14. The apparatus of claim 7, further comprising: a cover configured to
enclose at least a portion of the printed circuit board, a portion of the
cover defining, at least in part, the portion of the second flow path.

15. The apparatus of claim 7, wherein the inlet portion of the duct
includes a flow control member configured to adjust the magnitude of the
first portion of the cooling fluid relative to a magnitude of the second
portion of the cooling fluid.

16. An apparatus, comprising: a duct defining, at least in part, a
portion of a first inlet flow path, a portion of a second inlet flow path
and a portion of an exhaust flow path, the duct configured to be coupled
to a printed circuit board within a data processing unit such that a
first portion of a cooling fluid can flow within the first inlet flow
path from a source of cooling fluid to a first electronic device, a
second portion of the cooling fluid can flow within the second inlet flow
path from the source of cooling fluid to a second electronic device, and
the first portion of the cooling fluid can flow within the exhaust flow
path from the first electronic device to a volume within the data
processing unit apart from the second electronic device.

17. The apparatus of claim 16, wherein: the duct includes a side wall, a
first surface of the side wall defines, at least in part, the portion of
the second inlet flow path, a second surface of the side wall defines, at
least in part, the portion of the exhaust flow path.

18. The apparatus of claim 16, wherein: the first electronic device is an
optical transceiver disposed within a cage configured to contain a
plurality of optical transceivers in a stacked configuration; and the
duct includes a shroud defining an opening that faces towards a side wall
of the cage, an exterior surface of the shroud defining, at least in
part, the portion of the exhaust flow path, an interior surface of the
shroud defining, at least in part, the portion of the second inlet flow
path.

19. The apparatus of claim 16, wherein: the exhaust flow path is a first
exhaust flow path; and the duct defines, at least in part, a portion of a
third inlet flow path and a portion of a second exhaust flow path, the
duct configured to be coupled to the printed circuit board such that a
third portion of the cooling fluid can flow within the third inlet flow
path from the source of cooling fluid to a third electronic device and
the second portion of the cooling fluid can flow within the second
exhaust flow path from the second electronic device to a volume within
the data processing unit apart from the third electronic device.

20. The apparatus of claim 16, wherein: the duct defines a first opening
through which the first portion of the cooling fluid flows when the first
portion of the cooling exits the first inlet flow path, the first opening
defining a first flow axis; and the duct defines a second opening through
which the second portion of the cooling fluid flows when the second
portion of the cooling exits the second inlet flow path, the second
opening defining a second flow axis substantially coaxial to the first
flow axis.

Description:

BACKGROUND

[0001] The embodiments described herein relate to apparatus and methods
for cooling electronic devices, including, for example, air flow ducts
for directing cooling air flow to and/or away from an electronic device.

[0002] Data processing units, such as routers, switches, servers, storage
devices, and/or components included within a core switch fabric of a data
center, include electronic devices (e.g., amplifiers, signal processors,
optical transceivers or the like) that generate heat during their
operation. To increase the processing speed and/or processing capacity,
some known data processing units include high power electronic devices,
more densely-packaged electronic devices and/or the like. Accordingly,
some known data processing units include forced air cooling systems to
prevent overheating of the electronic devices contained within the known
data processing unit.

[0003] Some known cooling systems are configured to convey cooling air
across the surface of a circuit board via a cooling flow path that
extends from a first side the circuit board to a second side of the
circuit board. In such arrangements, however, the electronic devices
disposed on or adjacent the second side of the circuit board are exposed
to cooling air that has been heated as a result of flowing across the
electronic devices disposed on or adjacent the first side of the circuit
board. Similarly stated, with such cooling systems, the electronic
devices located downstream receive cooling air having a higher
temperature than that of the cooling air received by the electronic
devices located upstream. Moreover, such known cooling systems do not
allow the cooling air to be selectively directed toward or away from
certain electronic devices (e.g., electronic devices that are more
thermally-sensitive devices, electronic devices having high power
consumption or the like).

[0004] Thus, a need exists for improved apparatus and methods for cooling
air flow within data processing units.

SUMMARY

[0005] Air flow ducts for improving the air flow within data processing
units are described herein. In some embodiments, a duct includes an inlet
portion and an outlet portion. An interior surface of the outlet portion
of the duct defines, at least in part, a portion of a flow path. The duct
is configured to be coupled to a printed circuit board within a data
processing unit such that a first portion of a cooling fluid can flow
within the flow path between the inlet portion of the duct and an
electronic device coupled to the printed circuit board. An exterior
surface of the outlet portion of the duct is configured to redirect a
second portion of the cooling fluid to a volume within the data
processing unit apart from the electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 is a schematic illustration of a portion of a data
processing unit including a duct according to an embodiment.

[0007] FIG. 2. is a schematic illustration of portion of a data processing
unit according to an embodiment that defines multiple flow paths.

[0008] FIGS. 3 and 4 are perspective views of a portion of a data
processing unit including a duct according to an embodiment.

[0009] FIG. 5 is a side view of the portion of the data processing unit
shown in FIGS. 3 and 4.

[0010] FIG. 6 is a perspective view of a portion of the electronic device
assembly shown in FIGS. 3 and 4.

[0011] FIG. 7 is a perspective view of the duct shown in FIGS. 3 and 4.

[0012] FIG. 8-10 are a top view, a front view and a side view,
respectively, of the duct shown in FIGS. 3 and 4.

[0013] FIG. 11 is a cross-sectional view of the duct shown in FIGS. 3 and
4, taken along line X1-X1 in FIG. 8.

[0014] FIG. 12 is a cross-sectional view of the duct shown in FIGS. 3 and
4, taken along line X2-X2 in FIG. 8.

[0015] FIG. 13 is a cross-sectional view of the portion of the data
processing unit shown in FIGS. 3 and 4, taken along line X4-X4
in FIG. 4.

[0016] FIG. 14 is a cross-sectional view of the portion of the data
processing unit shown in FIGS. 3 and 4, taken along line X5-X5
in FIG. 4.

[0017] FIG. 15 is a cross-sectional view of the portion of the data
processing unit shown in FIGS. 3 and 4, taken along line X6-X6
in FIG. 4.

[0018] FIG. 16 is a cross-sectional view of the portion of the data
processing unit shown in FIGS. 3 and 4, taken along line X7-X7
in FIG. 5.

[0019] FIG. 17 is a cross-sectional view of the portion of the data
processing unit shown in FIGS. 3 and 4, taken along line X8-X8
in FIG. 5.

DETAILED DESCRIPTION

[0020] Air flow ducts for improving the air flow within data processing
units are described herein. In some embodiments, a duct includes an inlet
portion and an outlet portion. An interior surface of the outlet portion
of the duct defines, at least in part, a portion of a flow path. The duct
is configured to be coupled to a printed circuit board within a data
processing unit such that a first portion of a cooling fluid can flow
within the flow path between the inlet portion of the duct and an
electronic device coupled to the printed circuit board. An exterior
surface of the outlet portion of the duct is configured to redirect a
second portion of the cooling fluid to a volume within the data
processing unit apart from the electronic device.

[0021] In some embodiments, a duct includes an inlet portion, a first
outlet portion and a second outlet portion. The first outlet portion
defines, at least in part, a portion of a first flow path. The second
outlet portion has an exterior surface and an interior portion. The
exterior surface of the second outlet portion of the duct defines, at
least in part, a portion of the first flow path. The interior surface of
the second outlet portion of the duct defines, at least in part, a
portion of a second flow path. The duct is configured to be coupled to a
printed circuit board such that a first electronic device coupled to the
printed circuit board is within the first flow path, and a second
electronic device coupled to the printed circuit board is within the
second flow path. The first electronic device and the second electronic
device can be, for example, removable optical transceivers. The duct is
configured such that a first portion of a cooling fluid can flow within
the first flow path between the first electronic device and a volume
within the data processing unit apart from the second electronic device.
The duct is configured such that a second portion of the cooling fluid
can flow within the second flow path between the inlet portion of the
duct and the second electronic device.

[0022] In some embodiments, a duct defines, at least in part, a portion of
a first inlet flow path, a portion of a second inlet flow path, and a
portion of an exhaust flow path. The duct is configured to be coupled to
a printed circuit board within a data processing unit such that a first
portion of a cooling fluid can flow within the first inlet flow path from
a source of cooling fluid to a first electronic device. A second portion
of the cooling fluid can flow within the second inlet flow path from the
source of cooling fluid to a second electronic device. The first portion
of the cooling fluid can flow within the exhaust flow path from the first
electronic device to a volume within the data processing unit apart from
the second electronic device.

[0023] As used herein the term "data processing unit" refers to, for
example, any computer, electronic switch, switch fabric, portion of a
switch fabric, router, host device, data storage device, line card or the
like used to process, transmit and/or convey electrical and/or optical
signals. A data processing unit can include, for example, a component
included within an electronic communications network. In some
embodiments, for example, a data processing unit can be a component
included within or forming a portion of a core switch fabric of a data
center. In other embodiments, a data processing unit can be an access
switch located at an edge of a data center, or a host or peripheral
device (e.g., a server) coupled to the access device. For example, an
access switch can be located on top of a chassis containing several host
devices.

[0024] As used herein the term "electronic device" refers to any component
within a data processing unit that is configured to perform an electronic
function associated with the data processing unit. An electronic device
can include, for example, a switching device, a converter, a receiver, a
transmitter, a transceiver, a signal conditioner, an amplifier and/or the
like. In some embodiments, an electronic device can include an optical
transceiver configured to convert electrical signals into optical signals
and vice versa.

[0025] FIG. 1 is a schematic illustration of a portion of a data
processing unit 100 according to an embodiment. The data processing unit
100 includes a chassis (not shown), a printed circuit board 120, two
electronic devices 124A, 124B and a duct 150. The chassis or frame
defines an internal and/or enclosed volume that contains the printed
circuit board 120, electronic devices 124A, 124B, the duct 150 and any
additional components associated with the operation of the data
processing unit 100 (e.g., cooling fans, power supplies, data
transmission cables and/or the like). More particularly, the data
processing unit 100 and/or the chassis defines a volume 112 within which
the electronic devices 124A, 124B are disposed and a volume 114 that is
spaced apart from the volume 112. The volume 114 can include other
components of the data processing unit 100, such as, for example, other
electronic devices (e.g., devices having a different power consumption
and/or temperature sensitivity that the electronic devices 124A, 124B),
fans, power supplies and/or the like. The volume 112 and the volume 114
need not be separated by a distinct wall, baffle or structure, but can be
defined by the placement of the components therein. By segregating the
electronic devices 124A, 124B within the volume 112, an amount of cooling
air flow within the volume 112 can be provided to accommodate thermal
load and/or thermal sensitivity of the electronic devices 124A, 124B.

[0026] The printed circuit board 120 can be any suitable structure that
can operatively couple the electronic devices 124A, 124B to each other
and/or to other components within the data processing unit 100. In this
manner, the printed circuit board 120, the electronic devices 124A, 124B
and other electronic components (e.g., modules, connectors, and the like,
which are not shown in FIG. 1) can collectively perform, at least in
part, the functions of the data processing unit 100. In some embodiments,
for example, the printed circuit board 120 can be a substantially rigid
structure that includes a series of conductive layers surrounded by
and/or separated by an insulating material.

[0027] The electronic devices 124A, 124B are coupled to the printed
circuit board 120. In some embodiments, the electronic devices 124A, 124B
can be removably coupled to the printed circuit board 120. In some
embodiments, for example, the electronic devices 122A, 122B can be
pluggable optical transceivers. More particularly, the electronic devices
122A, 122B can be pluggable optical transceivers manufactured according
to the SFP standard or any other Multi-Source Agreement (MSA) standard,
including, for example, the Quad Small Form Factor Pluggable (QSFP)
standard, the CXP standard, the XFP standard, or the like.

[0028] The duct 150 includes an inlet portion 152 and an outlet portion
160. The inlet portion 152 of the duct 150 receives a first portion
F1 of a cooling fluid, as shown by the arrow AA in FIG. 1. The inlet
portion 152 can include, for example, one or more openings through which
the first portion F1 of a cooling fluid can enter the duct 150. The
cooling fluid can be any suitable cooling fluid (e.g., air, nitrogen, or
the like) used to cool the components within the data processing unit
100.

[0029] The outlet portion 160 of the duct 150 includes a side wall 161
having an interior (or inner) surface 162 and an exterior (or outer)
surface 163. The interior surface 162 defines, at least in part, a
portion of a flow path 141. The duct 150 is coupled to the printed
circuit board 120 such that the first portion F1 of the cooling
fluid flows within the flow path 141 between the inlet portion 152 of the
duct 150 and the electronic device 124A, as shown by the arrow BB in FIG.
1. Said another way, the duct 150 is coupled to the printed circuit board
120 such that the first portion F1 of the cooling fluid flows within
the flow path 141 between the inlet portion 152 of the duct 150 and the
volume 112 defined by the data processing unit 100 that includes the
electronic device 124A. Similarly stated, the first portion F1 of
the cooling fluid can be conveyed within the flow path 141 from the inlet
portion 152 of the duct 150 to the electronic device 124A. In this
manner, the first portion F1 of the cooling fluid flow can be
directed to the electronic device 124A via the duct 150 and/or the flow
path 141.

[0030] The exterior surface 163 of the outlet portion 160 is configured to
redirect a second portion F2 of the cooling fluid to the volume 114
spaced apart from the electronic devices 124A, 124B as shown by the arrow
CC in FIG. 1. Similarly stated, the exterior surface 163 of the outlet
portion 160 has a shape and/or orientation configured to change the flow
direction of the second portion F2 of the cooling fluid when the
second portion F2 of the cooling fluid flows against and/or adjacent
to the outlet portion 160 of the duct 150. More particularly, the
exterior surface 163 of the outlet portion 160 is shaped and/or oriented
to change the flow direction of the second portion F2 of the cooling
fluid from a first direction that would otherwise result in the second
portion F2 of the cooling fluid flowing into the volume 112 and/or
across the electronic device 124A to a second direction in which the
second portion F2 of the cooling fluid flows away from the volume
112 (e.g., into the volume 114) and/or away from the electronic device
124A. In this manner, the duct 150 can define at least in part, a portion
of a first flow path (e.g., the flow path 141) within which the first
portion F1 of the cooling fluid can flow into the volume 112 and/or
across the electronic device 124A, and can also redirect the second
portion F2 of the cooling fluid away from the volume 112 and/or the
electronic device 124A.

[0031] This arrangement can be used, for example, to provide a low
temperature, inlet cooling fluid to the electronic device 124A while also
redirecting a higher temperature, exhaust fluid produced by cooling the
electronic device 124B away from the electronic device 124A. For example,
as shown in FIG. 1, in some embodiments, the second portion F2 of
the cooling fluid can flow across, against and/or adjacent the electronic
device 124B before flowing across, against and/or contacting the outlet
portion 160 of the duct 150. Thus, when the second portion F2 of the
cooling fluid flows across, against and/or adjacent to the outlet portion
160 of the duct 150, it is an exhaust flow having a higher temperature
(as a result of cooling the electronic device 124B) than the first
portion F1 of the cooling fluid flowing within the duct 150. In this
manner, the first portion F1 of the cooling fluid, which is used to
cool the electronic device 124A, is not heated by and/or mixed with the
second portion F2 of the cooling fluid that is first used to cool
the electronic device 124B. Thus, the uniformity, efficiency and/or
effectiveness of a cooling system containing the duct 150 can be improved
as compared to cooling systems in which the air flows across the
electronic devices 124A, 124B in series.

[0032] Although the flow path 141 is shown as being defined substantially
entirely by the internal surface 162 of the outlet portion 160 of the
duct 150, in other embodiments, a duct and/or a portion of a duct can
define only a portion of a flow path. For example, in some embodiments, a
first portion of a flow path can be defined by a duct (similar to the
duct 150) and a second portion of the flow path can be defined by another
structure (e.g., the chassis). In other embodiments, a portion of a flow
path can be collectively defined by a duct (similar to the duct 150) and
another structure (e.g., the printed circuit board 120).

[0033] Although the exterior surface 163 of the outlet portion 160 is
shown and described above as redirecting the second portion F2 of
the cooling fluid to the volume 114 spaced apart from the electronic
devices 124A, 124B, in other embodiments, a portion of the duct 150
and/or the exterior surface 163 can define, at least in part a portion of
a flow path. For example, FIG. 2 is a schematic illustration of a portion
of a data processing unit 200 according to an embodiment. The data
processing unit 200 includes a chassis (not shown), a printed circuit
board 220, a first electronic device 224A, a second electronic device
224B, a duct 250 and a flow structure 280. The chassis or frame defines
an internal and/or enclosed volume that contains the printed circuit
board 220, the first electronic device 224A, the second electronic device
224B, the duct 250 and any additional components associated with the
operation of the data processing unit 200 (e.g., cooling fans, power
supplies, data transmission cables and/or the like). The data processing
unit 200 and/or the chassis defines a volume 212 within which at least
the second electronic device 224B is disposed and a volume 214 that is
spaced apart from the volume 212 that contains the second electronic
device 224B.

[0034] The printed circuit board 220 can be any suitable structure that
can operatively couple the first electronic device 224A and the second
electronic device 224B to each other and/or to other components within
the data processing unit 200. The printed circuit board 200 can be, for
example, similar to the printed circuit board 100 shown and described
above, and is therefore not described in herein. The first electronic
device 224A and the second electronic device 224B are coupled to the
printed circuit board 220, and can be, for example, removable optical
transceivers.

[0035] The duct 250 defines, at least in part, a portion of a first inlet
flow path 241, a portion of a second inlet flow path 242 and a portion of
an exhaust flow path 246. More particularly, a portion of the duct 250
and the baffle 280 collectively define the exhaust flow path 246. As
shown in FIG. 2, the duct 250 is coupled to the printed circuit board 220
such that a first portion F1 of a cooling fluid flows within the
first inlet flow path 241 from a source of cooling fluid (not shown in
FIG. 2) to the first electronic device 224A, as shown by the arrow DD in
FIG. 2. The first portion F1 of the cooling fluid flows the within
the exhaust flow path 246 from the first electronic device 224A to the
volume 214 that is spaced apart from the second electronic device 224B,
as shown by the arrow EE in FIG. 2.

[0036] The duct 250 is coupled to the printed circuit board 220 such that
a second portion F2 of the cooling fluid flows within the second
inlet flow path 242 from the source of cooling fluid (not shown in FIG.
2) to the second electronic device 224B, as shown by the arrow FF in FIG.
2. This arrangement allows the first portion F1 and the second
portion F2 of the cooling fluid to be conveyed to the first
electronic device 224A and the second electronic device 224B,
respectively, in parallel. Moreover, after the first portion F1 of
the cooling fluid flows across the first electronic device 224A, it is
directed away the second electronic device 224B. In this manner, the
second portion F2 of the cooling fluid, which is used to cool the
second electronic device 224B, is not heated by and/or mixed with the
first portion F1 of the cooling fluid that is first used to cool the
first electronic device 224A.

[0037] Although the exhaust flow path 246 is shown and described as being
collectively defined, at least in part, by the duct 250 and the baffle
280, in other embodiments, the exhaust flow path 246 can be defined
solely by the duct 250. Moreover, although the first intake flow path 241
and the second intake flow path 242 are shown in FIG. 2 as being separate
and/or distinct from each other, in other embodiments, a duct can define
a portion of a first intake flow path and a portion of a second intake
flow path that share a common boundary.

[0038] FIGS. 3 and 4 are perspective views of a portion of a data
processing unit 300 according to an embodiment. FIG. 5 is a side view of
the portion of the data processing unit 300. FIGS. 3 and 4 show the
portion of the data processing unit 300 without the top cover 315 to show
more clearly the components therein (the top cover 315 is shown, for
example, in FIG. 5). Additionally, certain components (e.g., the
connectors towards the rear of the printed circuit board 320) are shown
in FIG. 4 as a schematic representations. The data processing unit 300
includes a chassis (not shown), a printed circuit board 320, a series of
optical transceiver assemblies 322A, 322B, 322C and 332D and a cooling
system (not identified in FIGS. 3 and 4) that includes a duct 350.

[0039] The chassis or frame defines an internal and/or enclosed volume
that contains the printed circuit board 320, the optical transceiver
assemblies 322A, 322B, 322C and 332D, the duct 350, at least a portion of
the cooling system (e.g., cooling fans, plenums and/or the like) and any
additional components associated with the operation of the data
processing unit 300 (e.g., power supplies, data transmission cables
and/or the like). More particularly, the data processing unit 300 and/or
the chassis defines a first volume 312 within which the optical
transceiver assemblies 322A, 322B, 322C and 332D are disposed and a
volume 314 that is spaced apart from the volume 312. The volume 314 can
include other components of the data processing unit 300, such as, for
example, other electronic devices (e.g., devices having a different power
consumption and/or temperature sensitivity that the optical
transceivers), fans, power supplies or the like. By segregating the
optical transceiver assemblies 322A, 322B, 322C and 332D within the
volume 312 (i.e., outside of the volume 314), the cooling system and/or
the duct 350 can provide an amount of cooling air flow within the volume
312 to accommodate the thermal load and/or thermal sensitivity of the
optical transceiver assemblies 322A, 322B, 322C and 332D.

[0040] The printed circuit board 320 and the components mounted thereto
can be removably mounted within a specific "bay" defined within the
chassis. To facilitate this arrangement and to protect the printed
circuit board 320 and the components mounted thereto, the printed circuit
board 320 is substantially enclosed by a top cover 315 and a bottom cover
316, as shown in FIG. 5. Thus, the top cover 315 and/or the bottom cover
316 define, at least in part, the volume 312 and the volume 314.
Moreover, as described in more detail herein, the top cover 315 defines,
at least in part, a portion of the cooling flow paths within the data
processing unit 300.

[0041] The printed circuit board 320 can be any suitable structure that
can support and operatively couple the optical transceiver assemblies
322A, 322B, 322C and 332D to each other and/or to other components within
the data processing unit 300. In this manner, the printed circuit board
320, the optical transceiver assemblies 322A, 322B, 322C and 332D and
other electronic components (e.g., modules, connectors, and the like) can
collectively perform, at least in part, the functions of the data
processing unit 300. In some embodiments, for example, the printed
circuit board 320 can be a substantially rigid structure that includes a
series of conductive layers surrounded by and/or separated by an
insulating material.

[0042] Each of the optical transceiver assemblies 322A, 322B, 322C and
322D includes a mounting cage 325, as shown in FIG. 6, a series of
optical transceivers (not shown in FIG. 6), a series of electrical
connectors 323, As shown in FIG. 6, and a series of heat sinks 329 (see
e.g., FIGS. 14-17). The mounting cage 325 and the electrical connectors
323 are coupled to the printed circuit board 320 by a series of mounting
protrusions 371 and connector pins 372, respectively (only one protrusion
and one set of connector pins are identified for clarity). The mounting
cage 325 includes a side wall 326 that defines a partitioned interior
volume 327 within which a series (e.g., up to eight) of optical
transceivers can be removably disposed. More particularly, the interior
volume 327 is partitioned such that one optical transceiver can be
mounted between another optical transceiver and the printed circuit board
320. Similarly stated, the interior volume 327 is partitioned such that
optical transceivers can be removably coupled to the printed circuit
board 320 in a "stacked" configuration. Accordingly, each pair of optical
transceivers includes a top (or upper) optical transceiver mounted above
a bottom (or lower) optical transceiver that is mounted between the top
optical transceiver and the printed circuit board 320. Thus, the height
HC of the mounting cage 325 is at least two times the height of an
optical transceiver.

[0043] The side wall 326 of the mounting cage 325 defines a series
openings 328 through which a portion of a cooling fluid can flow, as
shown by the arrow GG in FIG. 6. Although not shown in FIG. 6, the side
wall opposite the side wall 326 also defines a series openings through
which a portion of a cooling fluid can flow (e.g., out of the interior
volume 327). In this manner, the portion of the cooling fluid can flow
laterally (or from one side to the other) through the bottom portion of
the interior volume 327 of the mounting cage 325. Similarly stated, this
arrangement facilitates the flow of cooling fluid across the top portion
of the bottom optical transceivers to cool the bottom optical
transceivers.

[0044] The mounting cage also defines a series of top openings (not shown
in FIG. 6) within which a series of heat sinks 329 (see e.g., FIGS.
14-17) are disposed and placed into contact with each of the top optical
transceivers. The heat sinks 329 can be any suitable structure that
facilitates the conduction and convection of heat from the optical
transceivers. For example, in some embodiments, the heat sinks 329 can be
similar to the "riding heat sinks" shown and described in U.S. patent
application Ser. No. 12/493,829, entitled "Heat Sinks Having a Thermal
Interface for Cooling Electronic Devices," filed on Jun. 29, 2009, which
is incorporated herein by reference in its entirety. Because a portion of
each of the heat sinks 329 is disposed above the mounting cage 325 (see
e.g. FIGS. 14-17), a portion of the cooling fluid can flow laterally (or
from one side to the other) across the top portion of the mounting cage
325, as shown by the arrow HH in FIG. 6. Thus, as described in more
detail herein, the cooling fluid flows in parallel across the top portion
of the mounting cage 325 and through the openings 328.

[0045] As shown in FIGS. 7-12, the duct 350 includes an inlet portion 352,
a central portion 354 and a three outlet portions 360A, 360B, 360C. As
described in more detail below, the duct 350 defines, at least in part a
first flow path 341, a second flow path 342 and a third flow path 343.
The first flow path 341 is shown in FIGS. 3, 7 and 8 as a dashed line.
The first flow path 341 includes an inlet portion 345 (defined, at least
in part, by the interior surface 362A of the outlet portion 360A) and an
exhaust portion 346 (defined, at least in part, by the exterior surface
363B of the outlet portion 360B). The second flow path 342 is shown in
FIGS. 7 and 8 as a dashed/dotted line. The second flow path 342 includes
an inlet portion 347 (defined, at least in part, by the interior surface
362B of the outlet portion 360B) and an exhaust portion 348 (defined, at
least in part, by the exterior surface 363C of the outlet portion 360C).
The third flow path 343 is shown in FIGS. 7 and 8 as a dotted line.

[0046] The inlet portion 352 of the duct defines an opening 351 through
which a cooling fluid can flow into the duct 350, as shown by the arrow
II in FIGS. 7 and 8. The size of the flow area AI (see FIG. 13)
defined by the inlet portion 352 decreases in the direction of the flow
(as indicated by the arrow II). Similarly stated the inlet portion 352 is
tapered such that, as shown in FIG. 8, the height HI of the inlet
portion 352 decreases in the direction of the flow. Although the flow
area AI is shown as having a substantially rectangular shape, in
other embodiments, the inlet portion 352 can have any suitable
cross-sectional shape (e.g., circular, oval or the like)

[0047] The central portion 354 of the duct 350 is disposed between and in
fluid communication with the inlet portion 352 and the three outlet
portions 360A, 360B, 360C. As shown in FIG. 14, the central portion 354
defines a flow area AC that is less than the flow area of the
opening 351 defined by the opening 351 of the inlet portion 352 and the
flow area AO of the openings (e.g., opening 366B as shown in FIG.
10) of the outlet portions 360A, 360B, 360C. Similarly stated, as shown
in FIG. 9, a height HC of the central portion 354 is less than a
height HI of the inlet portion 352 and/or a height HO of the
outlet portions 360A, 360B, 360C. More particularly, the height HC
of the central portion 354 is less than the distance between the surface
of the printed circuit board 320 and the top cover 315. In this manner,
as described in more detail below, the volume between the top cover 315
and the central portion 354 of the duct 350 can be within a portion of a
flow path. In particular, as shown in FIG. 7, the top cover 315 (not
shown in FIG. 7) and the central portion 354 of the duct 350 can
collectively define, at least in part, the exhaust portion 346 of the
first flow path 341 and/or the exhaust portion 348 of the second flow
path 342.

[0048] The outlet portions 360A, 360B, 360C of the duct 350 are
substantially similar, therefore where a description for a particular
outlet portion (e.g., outlet portion 360B) is provided below, that
description can also apply to the other outlet portions. In other
embodiments, however, a duct can include multiple outlet portions having
different characteristics (e.g., shape, size or the like) and/or
performance (e.g., flow performance).

[0049] Referring to FIGS. 7-12, each outlet portion 360A, 360B, 360C of
the duct 350 includes a shroud 364A, 364B, 364C (also referred to as a
hood or hooded portion) having a height HO (as identified for the
shroud 364B in FIG. 9). Each shroud 364A, 364B, 364C defines an opening
366A, 366B, 366C having a height H'O and defining a flow area
AO (as identified for the opening 366C in FIG. 10). The outlet
portions 360A, 360B, 360C of the duct 350 each include a side wall 361A,
361B, 361C having an interior (or inner) surface 362A, 362B, 362C and an
exterior (or outer) surface 363A, 363B, 363C.

[0050] As described above, the interior surface 362A defines, at least in
part, the inlet portion 345 of the first flow path 342. The interior
surface 362B defines, at least in part, the inlet portion 347 of the
second flow path 342. The interior surface 362C defines, at least in
part, a portion of the third flow path 343. The exterior surface 363B
defines, at least in part, the exhaust portion 346 of the first flow path
341. Moreover, the top cover 315 and the central portion 354 of the duct
350 also collectively define, at least in part, the exhaust portion 346
of the first flow path 341. The exterior surface 363C defines, at least
in part, the exhaust portion 348 of the second flow path 342. Moreover,
the top cover 315 and the central portion 354 of the duct 350 also
collectively define, at least in part, the exhaust portion 348 of the
second flow path 342.

[0051] The duct 350 is coupled to the printed circuit board 320 such that
the optical transceiver assembly 322A is disposed between the outlet
portion 360A and the outlet portion 360B, and the optical transceiver
assembly 322B is disposed between the outlet portion 360B and the outlet
portion 360C. Moreover, the duct 350 is coupled to the printed circuit
board 320 such that the opening 366A faces toward and/or is substantially
aligned with the optical transceiver assembly 322A, the opening 366B
faces toward and/or is substantially aligned with the optical transceiver
assembly 322B, and the opening 366C faces toward and/or is substantially
aligned with the optical transceiver assembly 322C. More particularly,
the opening 366A disposed adjacent the side wall 326 of the mounting cage
325 such that the portion of the cooling fluid that exits the opening
366A (as shown by the arrow JJ in FIGS. 7 and 8) flows laterally through
both the bottom portion of the interior volume 327 of the mounting cage
325 (as shown by the arrow GG in FIG. 6) and across, adjacent and/or
through the heat sinks 329 extending from the top of the mounting cage
325 (as shown by the arrow HH in FIG. 6).

[0052] The duct 350 is coupled to the printed circuit board 320 such that,
in use, a first portion of the cooling fluid flows within the inlet
portion 345 of the first flow path 341 between the inlet portion 352 of
the duct 350 and the optical transceiver assembly 322A, as shown by the
arrow JJ in FIGS. 7 and 8. Said another way, the duct 350 is coupled to
the printed circuit board 320 such that the first portion of the cooling
fluid flows within the first flow path 341 between the inlet portion 352
of the duct 350 and the volume 312 defined by the data processing unit
300 that includes the optical transceiver assembly 322A. The first
portion of the cooling fluid is then split into a portion that flows
laterally through the bottom portion of the interior volume 327 of the
mounting cage 325 and a portion that flows across, adjacent and/or over
the heat sinks 329 extending from the top of the mounting cage 325 as
described above with reference to FIG. 6. Similarly stated, at least a
portion of the optical transceiver assembly 322A is disposed within the
first flow path 341 such that the first portion of the cooling fluid
flows from the outlet portion 360A and through and/or across the optical
transceiver assembly 322A.

[0053] The first portion of the cooling fluid then flows from the optical
transceiver assembly 322A to the volume 314 within the data processing
unit 300 that is apart from the optical transceiver assembly 322A, as
shown by the arrow KK in FIGS. 7 and 8. Similarly stated, the first
portion of the cooling fluid then flows within the exhaust portion 346 of
the first flow path 341 to the volume 314. More particularly, the
exterior surface 363B of the outlet portion 360B is configured to
redirect the first portion of the cooling fluid to the volume 314.
Similarly stated, the exterior surface 363B of the outlet portion 360B
has a shape and/or orientation configured to change the flow direction of
the first portion of the cooling fluid as it exits the optical
transceiver assembly 322A. In this manner, the exterior surface 363B of
the outlet portion 360B redirects the exhaust flow from the optical
transceiver assembly 322A away from the optical transceiver assembly
322B. This arrangement prevents the first portion of the cooling fluid,
after having been heated by the optical transceiver assembly 322A, from
mixing with a second portion of the cooling fluid used to cool the
optical transceiver assembly 322B. This arrangement allows the cooling
fluid to be conveyed to the optical transceiver assemblies 322A and 322B
in parallel.

[0054] The duct 350 is coupled to the printed circuit board 320 such that,
in use, the second portion of the cooling fluid flows within the inlet
portion 347 of the second flow path 341 between the inlet portion 352 of
the duct 350 and the optical transceiver assembly 322B, as shown by the
arrow LL in FIGS. 7 and 8. Said another way, the duct 350 is coupled to
the printed circuit board 320 such that the second portion of the cooling
fluid flows within the second flow path 342 between the inlet portion 352
of the duct 350 and the volume 312 defined by the data processing unit
300 that includes the optical transceiver assembly 322B. The second
portion of the cooling fluid is then split into a portion that flows
laterally through the bottom portion of the interior volume 327 of the
mounting cage 325 and a portion that flows across, adjacent and/or over
the heat sinks 329 extending from the top of the mounting cage 325 (of
the optical transceiver assembly 322B) as described above with reference
to FIG. 6. Similarly stated, at least a portion of the optical
transceiver assembly 322B is disposed within the second flow path 342
such that the second portion of the cooling fluid flows from the outlet
portion 360B and through and/or across the optical transceiver assembly
322B. In some embodiments, the second portion of the cooling fluid can
have a flow direction when exiting the opening 366B that is substantially
coaxial to a flow direction of the first portion of the cooling fluid
when the first portion of the cooling fluid exits the opening 366A.
Similarly stated, in some embodiments, the opening 366B can define a
centroidal axis that is substantially coaxial to a centroidal axis of the
opening 366A.

[0055] The second portion of the cooling fluid then flows from the optical
transceiver assembly 322B to the volume 314 within the data processing
unit 300 that is apart from the optical transceiver assembly 322B, as
shown by the arrow MM in FIGS. 7 and 8. Similarly stated, the second
portion of the cooling fluid then flows within the exhaust portion 348 of
the second flow path 342 to the volume 314. More particularly, the
exterior surface 363C of the outlet portion 360C is configured to
redirect the second portion of the cooling fluid to the volume 314.
Similarly stated, the exterior surface 363C of the outlet portion 360C
has a shape and/or orientation configured to change the flow direction of
the second portion of the cooling fluid as it exits the optical
transceiver assembly 322B. In this manner, the exterior surface 363C of
the outlet portion 360C redirects the exhaust flow from the optical
transceiver assembly 322B away from the optical transceiver assembly
322C. This arrangement prevents the second portion of the cooling fluid,
after having been heated by the optical transceiver assembly 322B, from
mixing with a third portion of the cooling fluid used to cool the optical
transceiver assembly 322C. This arrangement allows the cooling fluid to
be conveyed to the optical transceiver assemblies 322B and 322C in
parallel.

[0056] The duct 350 is coupled to the printed circuit board 320 such that,
in use, the third portion of the cooling fluid flows within the third
flow path 343 between the inlet portion 352 of the duct 350 and the
optical transceiver assembly 322C, as shown by the arrow NN in FIGS. 7
and 8. Said another way, the duct 350 is coupled to the printed circuit
board 320 such that the third portion of the cooling fluid flows within
the third flow path 343 between the inlet portion 352 of the duct 350 and
the volume 312 defined by the data processing unit 300 that includes the
optical transceiver assembly 322C. The third portion of the cooling fluid
is then split into a portion that flows laterally through the bottom
portion of the interior volume 327 of the mounting cage 325 and a portion
that flows across, adjacent and/or over the heat sinks 329 extending from
the top of the mounting cage 325 (of the optical transceiver assembly
322C) as described above with reference to FIG. 6. Similarly stated, at
least a portion of the optical transceiver assembly 322C is disposed
within the third flow path 343 such that the third portion of the cooling
fluid flows from the outlet portion 360C and through and/or across the
optical transceiver assembly 322C. In some embodiments, the third portion
of the cooling fluid can have a flow direction when exiting the opening
366C that is substantially coaxial to a flow direction of the first
portion of the cooling fluid when the first portion of the cooling fluid
exits the opening 366A and/or a flow direction of the second portion of
the cooling fluid when the second portion of the cooling fluid exits the
opening 366B. Similarly stated, in some embodiments, the opening 366C can
define a centroidal axis that is substantially coaxial to a centroidal
axis of the opening 366A and/or a centroidal axis of the opening 366B.

[0057] In some embodiments, the duct 350 can be configured such that the
first portion of the cooling fluid (e.g., the portion that flows through
the outlet portion 360A to cool the optical transceiver assembly 322A),
the second portion of the cooling fluid (e.g., the portion that flows
through the outlet portion 360B to cool the optical transceiver assembly
322B) and/or the third portion of the cooling fluid (e.g., the portion
that flows through the outlet portion 360C to cool the optical
transceiver assembly 322C) are substantially equal. Similarly stated, in
some embodiments the duct 350 is "balanced" such that, in use, a
substantially equal amount of cooling flow is conveyed to each of the
optical transceiver assemblies 322A, 322B, 322C. In other embodiments,
however, the duct 350 can be balanced such that, in use, the flow rate of
the cooling fluid through at least one of the outlet portions (e.g., the
outlet portion 360A) is different from the flow rate of the cooling fluid
through one of the other outlet portions (e.g., the outlet portion 360B).

[0058] The balancing of the flow of cooling fluid within the duct 350 can
be accomplished by any suitable mechanism. For example, in some
embodiments, a size and/or a flow area of one of the outlet portions can
be different from a size and/or a flow area of one of the other outlet
portions. For example, in some embodiments, the flow area of the outlet
portion 360C, which is furthest from the inlet portion 352 of the duct
350, can be larger than the flow area of the outlet portion 360A, which
is closest to the inlet portion 352 of the duct 350. This arrangement can
produce a substantially equal flow rate of cooling fluid through the
outlet portions 360A and 360C by accommodating for differences in
frictional losses resulting from the difference in the length of the
first flow path 341 and the third flow path 343. In other embodiments, a
duct can include a flow control member (e.g., a valve, a baffle, an
orifice or the like) to balance selectively the flow of cooling fluid
within the duct.

[0059] In some embodiments, at least one of the outlet portions 360A,
360B, 360C can include a flow control member, such as, for example, a
baffle, to redirect and/or balance the flow of cooling fluid into and/or
around the adjacent optical transceiver assembly. For example, in some
embodiments, the outlet portion 360A can include one or more baffles (not
shown in FIGS. 7-12) coupled to the interior surface 362A adjacent the
opening 366C. The baffle or baffles can have a shape and/or orientation
to subdivide the first portion of the cooling fluid into a portion that
flows through the bottom portion of the interior volume 327 of the
mounting cage 325 via the openings 328 (as shown by the arrow GG in FIG.
6) and a portion that flows across the top portion of the mounting cage
325 (as shown by the arrow HH in FIG. 6). In some embodiments, for
example, the outlet portion 360A can include a baffle or baffles having a
shape and/or orientation such that the flow through the openings 328 is
different than the flow across the top of the mounting cage 325.

[0060] The ducts shown and described herein, such as, for example, the
duct 350 can be constructed from any suitable material. Such materials
can include, metal, plastic and/or composite materials. In some
embodiments, a duct of the types shown and described herein can be
constructed from more than one material. For example, in some
embodiments, a duct can include a metallic substrate and/or structural
layer material and an thermally insulative layer (e.g., constructed from
fiberglass, a foam polymer or the like). Moreover, any of the ducts shown
and described herein can be monolithically constructed or constructed
from multiple components that are later joined together.

[0061] The data processing units are shown and described above as
including one or more sources of cooling fluid. Such sources of cooling
fluid can be any suitable source of cooling fluid, such as, for example,
a fan tray, a compressed gas tank, a plenum containing pressurized air or
the like. In some embodiments, for example, the source of cooling fluid
can include a propeller fan, a tubeaxial fan and/or a vaneaxial fan for
producing a pressurized air flow through the data processing unit. For
example, in some embodiments, a source of cooling fluid can be a fan can
be any suitable tubeaxial fan produced by Delta Electronics, Inc. (e.g.,
the QFR 60×60×38 Series tubeaxial fan), EBM-Papst, Inc.
(e.g., the 3000 Series tubeaxial fan) and the Nidec Servo Corporation
(e.g., the PUDC series tubeaxial fan).

[0062] While various embodiments have been described above, it should be
understood that they have been presented by way of example only, and not
limitation. Where methods and/or schematics described above indicate
certain events and/or flow patterns occurring in certain order, the
ordering of certain events and/or flow patterns may be modified. While
the embodiments have been particularly shown and described, it will be
understood that various changes in form and details may be made.

[0063] For example, although air is the cooling medium described herein
(e.g., the flow paths are often referred to as "air" flow paths), in
other embodiments, any suitable gas can be used as the cooling medium.
For example, in some embodiments, the cooing medium can be nitrogen.

[0064] Although the ducts shown and described herein (e.g., duct 350) have
been shown as being a fully enclosed structure having at least one inlet
opening (e.g., opening 351) and at least one outlet opening (e.g.,
opening 366A), and defining at least one flow path (e.g., flow path 341)
therein, in other embodiments, a duct can be any structure that can
define a flow path, flow conduit, flow channel and/or that can redirect
an air flow as described herein. For example, in some embodiments, a duct
can include a structure that is not fully enclosed. For example, in some
embodiments, a duct can be a structure similar to the duct 350, but
having an open bottom portion. Accordingly, when the duct is coupled to a
printed circuit board, the side wall of the duct and the surface of the
printed circuit board collectively define at least a portion of a flow
path, flow conduit and/or flow channel. In other embodiments, a duct can
include one or more baffles or other flow structures coupled to a printed
circuit board that collectively define a flow path and/or redirect a flow
of cooling fluid (e.g. similar to a series of stator blades)

[0065] Although the duct 350 is shown as having one inlet portion 352 and
three outlet portions 360A, 360B and 360C, in other embodiments, a duct
can have any number of inlet portions and any number of outlet portions.
For example, in some embodiments, a duct can include two inlet portions
and four outlet portions. In some such embodiments, one of the inlet
portions can be in fluid communication with two of the outlet portions,
and the other inlet portion can be in fluid communication with the other
two outlet portions.

[0066] Although the duct 350 is shown and described above as including
three substantially similar outlet portions 360A, 360B, 360C, in other
embodiments, a duct can include any number of outlet portions, where at
least one of the outlet portions differs in size, shape and/or function
from at least one of the other outlet portions.

[0067] Although various embodiments have been described as having
particular features and/or combinations of components, other embodiments
are possible having a combination of any features and/or components from
any of embodiments as discussed above. For example, in some embodiments,
a data processing unit can include a duct similar to the duct 350 (shown
and described with reference to FIGS. 7-12) and a baffle similar to the
baffle 280 (shown and described with reference to FIG. 2).